Liquid crystal display elements now in practical use include a twisted nematic (TN) mode and a super twisted nematic (STN) mode. Display cells utilizing ferroelectric liquid crystals have also been proposed. These display cells essentially contain a polarizing sheet and require orientation treatment.
There is also known a process for producing a liquid crystal device capable of making a large, bright, and high contrast display at low cost without requiring a polarizing sheet or orientation treatment, in which a polymer matrix having dispersed therein encapsulated droplets of a liquid crystal material is formed into a thin film (hereinafter referred to as a polymer-encapsulted type device) as disclosed in JP-A-58-501631 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") and U.S. Pat. No. 4,435,047. The encapsulating material proposed includes gelatin, gum arabic, polyvinyl alcohol, etc.
According to this technique, when liquid crystal molecules encapsulated with polyvinyl alcohol exhibit positive dielectric anisotropy in a film, they are orientated in the direction of an electric field in which they are placed, and exhibits transparency if a refractive index n.sub.o of the liquid crystal is equal to a refractive index n.sub.p of the polymer. On removal of the electric field, the liquid crystal molecules are not aligned and the refractive index of the liquid crystal droplets is shifted from n.sub.o. As a result, light is scattered at the interface of liquid crystal droplets and inhibited from transmission to make the film white turbid.
There are several other proposals using a polymer film having dispersed therein microcapsulted liquid crystal droplets. For example, JP-A-61-502128 discloses liquid crystals dispersed in an epoxy resin, and JP-A-62-2231 discloses liquid crystals dispersed in a specific ultraviolet-cured polymer.
The characteristics demanded for the aforesaid large-area liquid crystal devices in application to practical use are (1) that they can be driven at a low voltage; (2) that they provide a display of sufficient contrast; and (3) that they can be applied to a multiplexing drive system.
The characteristics (1) and (3) are of particular importance for reducing the cost incurred for the driving part of the device. However, there has not yet been developed a liquid crystal device which does not need a polarizing sheet and still-meet these requirements.